1. Field of the Invention
The present invention relates to an image taking apparatus. More specifically, it relates to a technique for eliminating electromagnetic interference (EMI).
2. Description of the Related Art
There is an increasing demand for digital cameras, such as digital still camera and digital video camera, that incorporate a solid-state image sensor, such as charge coupled device (CCD) and complementary metal oxide semiconductor (CMOS).
In recent years, solid-state image sensors are improved in resolution, and accordingly, digital cameras are required to read image signals from a solid-state image sensor at higher clock frequency to read image signals at higher rate.
A conventional digital camera, which drives the solid-state image sensor at a clock frequency of 30 MHz, does not have a problem of EMI. However, if the clock frequency is raised to 60 MHz or higher, there arises a problem that an electromagnetic wave higher than the criterion level occurs via the taking lens of the digital camera.
Although the drive circuit for driving the solid-state image sensor generates the strongest electromagnetic wave, the electromagnetic wave can be blocked by surrounding the drive circuit with a shielding member. However, there remains a problem that the electromagnetic wave generated from the front of the solid-state image sensor driven by the drive circuit cannot be blocked by the shielding member because the optical path for picture taking has to be ensured.
In order to solve the problem, there have been proposed a solid-state image sensor module for an endoscope and an image taking apparatus that have an optically-transparent electromagnetic shielding layer on the light-receiving surface of the solid-state image sensor.